The present invention relates to a device and a method for moving a joint and, more specifically, to a device and method for passively exercising a patient""s joint in effort to return the joint to a more natural range of motion.
Patients who have suffered damage to tendons, soft tissue, or bone near a joint, either from trauma or disease, are frequently advised to adhere to an exercise regime to prevent the loss of mobility in the joint. Often, the exercise regime requires a physical therapist or a complex and expensive machine, such as a continuous passive motion (CPM) machine to repeatedly move the joint. With many patients, however, the inconvenience of attending to such treatments severely affects the time that such therapy is administered.
Another problem to effective treatment is that many exercise regimes require motivation, diligence, and perseverance on the part of the patient. For example, inactivity during the night causes many patients with arthritis or other types of joint stiffness to experience a decrease in the range of motion of an affected joint. As a result, such patients are often advised to spend a certain amount of time each morning manually moving and bending the affected joint. Although the prescribed exercise program is intended to restore the joint to its natural range of motion, patients often fail to perform the necessary exercises due to pain, frustration, or inconvenience. This is a significant drawback with a manual exercise treatment that requires a high level of patient compliance in order to be effective.
Accordingly, different types of passive movement devices have been employed. Such devices typically exercise a joint by flexing and/or extending the joint using inflatable members, such as pouches, bladders, or sacs, which are attached to the joint. Movement is effected by cyclically inflating and deflating the inflatable members with gas, fluid, or heated fluid. However, such positive pressure devices are not always practical and are not always effective in applying a suitable force during deflation of the bladder to properly exercise the joint. Additionally, there is an attendant risk that the inflatable member will burst during use.
In other conventional devices, the joint is alternately flexed and extended by attaching inflatable members to both the flexion and extension sides of the joint. The joint is then systematically flexed and extended by cyclically inflating one of the inflatable members and deflating the other inflatable member in a synchronous manner. however, such systems require precise timing of inflation and deflation of the inflatable members to apply suitable pressure for effective treatment.
In other conventional devices, the joint is alternately flexed and extended by attaching inflatable members to both the flexion and extension sides of the joint. The joint is then systematically flexed and extended by cyclicly inflating one of the inflatable members and deflating the other inflatable member in a synchronous manner. However, such systems require precise timing of inflation and deflation of the inflatable members to apply suitable pressure for effective treatment.
One method of avoiding the difficulties associated with the use of multiple inflatable members has been to use a spring steel element to bias the joint into the non-extended position, in conjunction with the use of an inflatable pouch positioned on the extension or outer side of the joint to bias the joint into the extended position. In operation, the joint is extended by inflating the pouch. The joint is then flexed by deflating the pouch and allowing the spring steel element to return the joint to the flexed position. However, with certain patients, the spring steel biasing element may apply excessive forces at points of connection or attachment to the patient""s joint. In addition, it is difficult to control or regulate the application of the force to achieve more uniform pressure to tissues surrounding the joint.
In light of the foregoing, it would be desirable to provide a device for passively exercising a joint wherein the device is biased to the neutral or extended position in such a manner that the biasing force is exerted uniformly to the underlying tissue without the use of positive pressure devices such as inflatable bladders.
The present invention relates to a passive movement device for moving or exercising a selected joint or joints of a patient. The device is secured into proper position at or about a selected joint and is then operated to move or exercise the patient""s joint in a controlled manner. The passive movement device comprises a resilient, open-cell foam section and a flexible cover or casing that functions to enclose the foam section to form a sealed chamber. Joint positioning means is used to maintain the joint to be treated at a desired position in relation to the device. For example, hand and finger slots may be provided in the foam section to effect proper retention and positioning of a patient""s hand. Alternatively, a glove may be fixedly or removably attachable to the sealed chamber to properly hold the patient""s hand in position. In applications in which another joint such as a patient""s elbow is being treated, a sleeve may be used to secure the sealed chamber at the elbow joint.
A pump in the form of a vacuum pump is operatively connected with the sealed chamber to supply a reduced pressure, i.e. below atmospheric pressure, to the sealed chamber. The application of reduced pressure to the sealed chamber, for example, during the xe2x80x9conxe2x80x9d cycle of the pump, collapses the pores in the foam section thereby collapsing or contracting the sealed chamber against the resiliency of the foam section in a controlled manner dependant on the amount and timing of the suction. Collapsing the sealed chamber exerts a force on the joint causing the joint to bend from a first or neutral position, i.e. a relaxed position between full extension and full bending. Since the pores are distributed throughout the foam section, the force is exerted generally uniformly to the underlying tissue. The suction may then be removed, for example during the xe2x80x9coffxe2x80x9d cycle of the pump, causing the foam section to expand back toward its original position, due to the resiliency of the foam section, thereby causing the joint to bend back toward the first or neutral position.
The foam section may comprise any of a number of commercially available materials, such as a sponge, having an open-cell structure. The foam section provides a resilient member for returning the sealed chamber to its uncollapsed position when the suction supplied by the vacuum is sufficiently reduced or removed. The porosity and resiliency of the foam section can be chosen for particular uses. For example, a foam section having smaller pores or cells provides a greater biasing force and, therefore, may be preferred when treating a particularly stiff joint. Conversely, when a weaker force will suffice, a more compressible foam section may be preferred. In addition, the foam section may comprise two or more adjoining sections having different degrees of stiffness.
The foam section can be provided in a variety of sizes and shapes to fit the individualized needs of a particular patient. The foam section may be shaped to comfortably fit along the flexion or inner side of the joint when the joint is in either the neutral or the extended position. Alternatively, the foam section can be shaped to conform to the extension or outer side of the joint when the joint is in either the neutral or the flexed position.
The cover or casing for enclosing and sealing the foam section can be formed of a plastic laminate or sheet which is wrapped or folded around the foam section to provide the sealed chamber. Additionally, the cover can be molded around the foam section to form the sealed chamber. The cover can be manufactured of any of a variety of materials, such as polyruethane films, provided that the material is substantially gas-impermeable and sufficiently flexible to contract and stretch during the application and non-application of the reduced pressure to the sealed chamber. Alternatively, the cover can be formed by coating the outer surface of the foam section with a substance which is sufficiently flexible or substantially gas-impermeable, or by otherwise sealing the pores on the outer surface of the foam section, such as by heat sealing.
The joint positioning means can include grooves or holes which are appropriately shaped within the foam section to accommodate the selected joint and hold the device in position on the joint. For example, the positioning means may include finger or hand holes in the foam section. Alternatively, the positioning means can comprise a glove or a mitten, or selected portions thereof, which is attachable with the sealed chamber to maintain the sealed chamber in the desired position relative to the joints to be treated. The glove or mitten may be made from a porous material, such as cotton, for the patient""s comfort. Securing means such as straps or belts can be provided to maintain the device in the desired position relative to the patient""s joint.
Suction means is provided in the form of a vacuum pump connected with the cover of the sealed chamber by a fluid transmission tube. The tube is in fluid communication with the sealed chamber to enable the reduced pressure to be supplied to the sealed chamber. One end of the tube is positioned within the sealed chamber and may be embedded within the foam section. The other end of the tube is external of the sealed chamber and connects with the vacuum pump.
One or more struts may optionally be utilized for reinforcing the foam section at selected positions relative to the patient""s joint. The strut may be in the form of a rigid or semi-rigid rod of suitable material, such as wood or plastic, which is embedded in the foam section. The strut may be disposed within the foam section so as to be positioned on the inner side of the joint and to extend in a transverse direction relative to the joint. The strut functions to restrict the contraction of the foam section in a direction parallel to the strut, thereby reducing forces on the joint transverse to the direction in which the joint bends. As such, the strut facilitates the proper bending of the joint around the strut.
Particularly stiff joints may require a greater force to return the joint back to the neutral position than the force that is supplied by the foam section resiliently returning to its original shape. In such cases, sealed chambers incorporating separate foam sections may be positioned on both sides of the joint. Accordingly, a first foam section enclosed in a first sealed chamber is positioned at the outer or extension side of the joint and a second foam section enclosed in a second sealed chamber is positioned at the inner or flexion side of the joint. When the joint is in a flexed or neutral position, suction is applied to the first sealed chamber and is removed from the second sealed chamber so that the first foam section collapses and the second foam section expands causing the joint to extend. Alternatively, suction is applied to the second sealed chamber and is removed from the first sealed chamber so that the second foam section collapses and the first foam section expands causing the joint to flex. The use of the two sealed chambers enables the joint to more easily flex and extend from the neutral position.
The present invention also relates to a method for passively exercising a patient""s joint. A device, comprising a foam section and a casing enclosing the foam section within a sealed chamber, is positioned at the desired location relative to the joint to be exercised. The device may, for example, be positioned at the flexion or inner side of the joint.
A reduced pressure is then applied to the sealed chamber at a controlled rate and at a controlled magnitude of vacuum. The application of reduced pressure to the sealed chamber causes the pores of the foam section to collapse at a predetermined rate, thereby applying a predetermined force to the joint to produce a predetermined range of motion in the joint. When the foam section is positioned on the inner side of the joint, the application of suction to the sealed chamber causes the joint to bend from its neutral or its extended position.
After the foam section has been collapsed and the joint has been moved, the reduced pressure within the sealed chamber is released. As the pressure returns to atmospheric pressure, the foam section returns to its original shape and size. As the foam section expands, a force is exerted on the joint causing the joint to return to its neutral or its extended position.
The controlled rate of collapse and the controlled magnitude of the applied pressure allow the joint to be moved in a manner which is best suited for each individual patient. For example, joints at the start of treatment are apt to be stiffer and require a greater force to move the joint, thus a higher vacuum may be used initially to evacuate the chamber. Also at the start of treatment, the patient may experience more pain with joint movement and, hence, a slower rate of movement may be better to minimize the amount of associated pain. Accordingly, the vacuum may be applied at higher magnitudes of pressure but at less frequent intervals at the start of treatment.